Background: Expressing caries prevalence as mean DMFT value dose not correctly reflects the skewed distribution, leaving high caries groups undiscovered in the population, based on these features, a new index called Significant Caries Index (SiC) was proposed by WHO to draw attention to individuals with the highest caries scores in each population. Aims: The aim of this study was to compare the caries prevalence and severity in school children living in rural and urban areas. Methods: The sample examined in this study consisted of 414 school children in rural and 414 school children in urban areas. All children were subjected to clinical examination to obtain information about dental caries prevalence and severity in permanent dentition DMFT/DMFS according to WHO 1997. Also, information was obtained about dental caries status in primary dentition dmft/dmfs according to Gruebbell. Significant caries index (SiC) was calculated for primary and permanent dentition. Data collection started from 20th January 2018 to 20th March 2018. Data were analyzed using a statistics package for SPSS version 24 for Windows and Excel 2007. Results: The prevalence of dental caries in permanent teeth in urban and rural areas was 56.8%, 77.6%, respectively. The mean value of DMFT in urban and rural areas was (1.40 ± 0.42), (2.24 ± 1.53) respectively. Also, statistical analysis showed significant differences between the mean value of dmfs/DMFS in an urban and rural area as well as analysis of variance showed a significant difference between the value of significant caries index (SiC) in urban (4.0) and rural (3.5) areas. Conclusions: The caries prevalence, severity, and the significant caries index (SiC) of primary and permanent dentition was higher in school children living in rural areas than in school children living in urban areas.